Recently, patent foramen ovale (hereinafter referred to as PFO) has been identified as a cardiac factor in strokes and migraines. The PFO is a symptom in which the oval foramen (foramen ovale) for shortcircuiting blood between the left and right sides in the heart in the fetal period of a person's life remains even after the person has gown up. It is said that 20-30% of grown-up people have this disease.
The PFO is generated in the septum secundum (hereinafter referred to as SP) of a heart. In a heart at normal time, the blood pressure in the left atrium of heart is higher than that in the right atrium of heart, so that the oval foramen is closed with the septum primum (hereinafter referred to as SP). However, when the blood pressure in the right atrium of the heart exceeds that in the left atrium of heart in certain circumstances (for example, at the time of coughing or straddling), the SP opens to the side of the left atrium of heart, resulting in blood flow from the side of the right atrium of heart (the vein side) to the side of the left atrium of heart (the artery side). If thrombi are contained in the blood in this case, the thrombi are transferred from the vein side to the artery side, and flow from the left atrium of heart into the left ventricle, then into the aorta and into the brain, possibly causing a stroke or migraine.
Examples of the treatment of such a disease include pharmacotherapy (aspirin, warfarin, or the like), closure of the PFO by percutaneous catheterization, and open heart surgery by extracorporeal circulation. Pharmacotherapy is the treatment which should be selected first, but it can be difficult to manage the dosage, and bleeding may not cease easily during the dosage. Percutaneous catheterization and the open heart surgery are radical treatments and remove the fear of recurrence, though they are invasive procedures. At the present stage, of these closure procedures, open heart surgery is more assured. However, taking into account the risk attendant on the extracorporeal circulation and the magnitude of the invasion attendant on skin incision, the treatment by percutaneous catheterization is more desirable, if it produces the same effect as that of the open heart surgery.
Devices for closure by use of percutaneous catheterization can be used also in the cases of closing a defect, such as cogenital atrial septal defect (ASD), PFO, ventricular septal defect (VSD), patent ductus arteriosus (PDA), etc. The conventional devices, however, are based on clamping the SP and the SS by use of a disk-like membrane or anchor member for closing the defect, and they are left indwelling in the patient's body.
The membrane and the anchor member are foreign matters for the body, and thrombi are liable to deposit thereon. Particularly, when a thrombus deposits on the disk-like membrane on the side of the left atrium of the heart, it may flow downstream to cause stroke, or may break the SP which is small in wall thickness. In addition, these members may be positionally deviated, instead of being positionally fixed in the state of clamping the relevant tissues.
In view of these points, recently, there has been proposed the PFO closing device as described in WO2004/086944 A2 (refer to Abstract, FIG. 10, etc.).
In use of this PFO closing device, the appliance is passed through the PFO from the right atrium of heart toward the left atrium of heart, the SP is drawn to the PFO to close the latter, and energy is applied thereto so as to join the tissues to each other.